The present invention relates to a pneumatic valve and, more particularly, to an electrically-operated pneumatic valve incorporating a poppet seal.
Conventional electrically-operated plunger-type valves include a housing with a transverse passage formed therein, which is in communication with a primary or inlet port, a secondary or outlet port, and a discharge or exhaust port. A plunger is received in the transverse passage of the housing for movement along the passage, with the movement of the plunger controlling the communication between the ports and, thereby, opening and closing the valve. The plunger is moved by an electromagnetic actuator, which is also mounted in the housing. When an electric current is applied to the electromagnetic actuator, an electromagnetic field is generated which moves the plunger along the transverse passage to vary the communication between the ports. Positioned between the plunger and the fixed seat of the valve, is a poppet which seals against the valve seat to control the flow of fluid through the valve.
The mechanism for sealing a conventional poppet in its closed position is to use a heavy spring force to compress the poppet against the mating fixed valve seat with enough force to overcome the force of the compressed air that is trying to push its way between the poppet and the valve seat. The main disadvantage to this method is it takes a relatively large amount of electrical energy to generate a magnetic force sufficient to overcome the heavy spring force when it is desired to open the valve. The greater the spring force, the greater the electrical energy that is required to operate the valve. A disadvantage of these energy requirements is an undesirable heat byproduct when the valve is in operation. This is particularly problematic when the valve is used near electronic devices, which are sensitive to heat.
Consequently, there is a need for an electrically-operated plunger-type valve which can operate while consuming less power than conventionally known solenoid valves so that the valve can be used in a heat sensitive environment.
The present invention provides a valve assembly which consumes less power than conventionally known poppet design valves. Furthermore, the present invention provides a valve assembly which can achieve higher flow rates than conventionally known poppet designs.
In one form of the invention, an electrically-operated plunger-type valve assembly includes a housing, an electromagnetic actuator which is positioned in an interior chamber of the housing, and a plunger assembly also positioned in the interior chamber of the housing. The plunger assembly is supported for reciprocal axial movement in the interior chamber between a first position and a second position. The housing includes an inlet port and an outlet port, and a communication passage between the inlet port and the outlet port. The communication passage is open to permit communication between the inlet port and the outlet port when the plunger assembly is moved to its first position thereby opening the valve assembly. When the plunger assembly is moved to its second position, the communication passage is closed between the inlet port and the outlet port whereby the valve assembly is closed. The valve assembly also includes a biasing member which applies a spring force to the plunger assembly to urge the plunger assembly to its second position, with the electromagnetic actuator selectively generating a magnetic field having sufficient magnitude to move the plunger assembly against the force of the biasing spring to move the plunger assembly to its first position when the electromagnetic actuator is energized to selectively move the plunger assembly between its first and second positions to control the communication between the inlet port and the outlet port. The plunger assembly has a seal member which seals the communication passage to close communication between the inlet port and the outlet port when the plunger assembly is moved to its second position. The seal member is acted upon by pressurized fluid in the inlet port to radially seal against the communication passage whereby the spring force of the biasing member can be reduced which in turn reduces the amount of energy needed to move the plunger assembly between its first and second positions.
In one aspect, the seal member includes a projecting member, which radially sealingly engages the communication passage to close communication between the inlet port and the outlet port when the plunger assembly is moved to its second position. In a further aspect, the projecting member deflects radially outward to sealingly engage the communication passage. For example, the projecting member may comprise an annular lip.
In another aspect, the housing further includes an exhaust port, with the communication passage extending between inlet port, the outlet port, and the exhaust port. The seal member sealingly engages a first portion of the communication passage when the plunger assembly is in the first position to seal off the exhaust port and open communication between the inlet port and the outlet port to thereby open the valve assembly. The seal member sealingly engages a second portion of the communication passage when the plunger assembly is in its second position to seal off communication between the inlet port and the outlet port.
In a further aspect, the seal member comprises a unitary seal and includes a first sealing surface for sealingly engaging the first portion and a second sealing surface for sealingly engaging the second portion. Furthermore, at least one of the sealing surfaces comprises a projecting lip. In a preferred form, both the first and second sealing surfaces comprise projecting lips.
According to another form of the invention, an electrically-operated plunger-type valve assembly includes a housing, an electromagnetic actuator which is positioned in an interior chamber of the housing, and a plunger assembly which is also positioned in the interior chamber and supported for reciprocal axial movement in the interior chamber between a first position and a second position. The interior chamber includes communication passages between an inlet port, an outlet port, and an exhaust port. When the plunger assembly is moved to the first position, the communication passage between the inlet port and the outlet port is open thereby opening the valve assembly. When the plunger assembly is moving to its second position, the communication passages between the inlet port and the outlet port and the exhaust port are open. When the plunger assembly is moved to its second position, the communication passages between the inlet port and the outlet port and the exhaust port are closed. The valve assembly also includes a biasing member which applies a spring force to the plunger assembly to urge the plunger assembly to its second position. The electromagnetic actuator generates a magnetic field having sufficient magnitude to move the plunger assembly against the force of the biasing member to move the plunger assembly to its first position when the electromagnetic actuator is energized to selectively move the plunger assembly between its first and second positions to control opening and closing of the valve assembly. The plunger assembly has a sealing member with first and second sealing surfaces for sealing the communication passage when in its first and second positions, respectively. At least the second sealing surface radially sealingly engages the communication passage and is acted upon by pressurized fluid in the inlet port to radially seal against the communication passage whereby the spring force of the biasing member can be reduced which in turn reduces the amount of energy need to move the plunger assembly between its first and second positions.
In one aspect, at least one of the sealing surfaces comprises a flexible lip. In a further aspect, second sealing surface comprises a flexible lip. In a further aspect, the flexible lip deflects radially outward to sealingly engage the second portion of the communication passage. In yet a further aspect, the sealing member includes an annular groove radially inward of the flexible lip whereby the pressure of the pressurized fluid enters the annular groove to urge the second sealing surface to deflect radially outward to sealingly engage the second portion of the communication passage. In this manner, a seal between the sealing member and the communication passage can be achieved with a lower spring force, thereby reducing the power requirements of the valve assembly.
These and other objects, advantages, purposes, and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings.